In the parent application internal and/or external surfacing of tubes having as cross section any closed ring and of calibration from the inside or from the outside of said tubes is described characterized by the fact that there is used to work, a tool or mandrel of which one part at least of the external surface, harder than the metal to be worked, is defined by the displacement of a meridian curve resting on a closed directrix approximately identical with the border corresponding to the surface to be worked of the cross section of the tube. The profile of the tool along a meridian curve generating its external surface is such that, when passing from the first end plane of the tool, which corresponds to the point at which the tool enters in contact with the tube, to the second end plane of the tool, which corresponds to the plane at which the end of the contact occurs between the tool and the tube, there is made to vary in a continuous manner the distance to the axis of the tube, increasing it when work is done on the internal surface of the tube, and decreasing it when work is done on the external surface. The maximum variation of said distance is greater than the maximum depth of the faults which the tube presents on the surface to be worked on, and smaller than the value which corresponds, to insure the displacement of the tool along the axis of the tube, with a force applied on the tube which exceeds the mechanical resistance of said tube, and in that there is insured a relative displacement in translation along the axis of the tube between the above defined tool and the tube to be worked on.
In a preferred mode of operation defined in the parent application, it has been suggested to perform the calibrating and the internal surfacing of a tube having a circular section by means of a mandrel having the shape of a toric ring with a half round section. It has been indicated that, in the case when work is done on cold drawn steel tubes, the radius of the cross section of the toric mandrel had to be, for the first run of the work preferably between 3 and 6 mm, but could be more, for example, 10 mm, for the finishing run. It has also been indicated that the tube to be worked is preferably subjected to a preliminary run through a drawplate to perform a shaping of the tube. It has finally been indicated that at the time of the running of the toric mandrel inside the tube, it is necessary generally to lubricate the inside of the tube and/or the mandrel. The suggested lubricating is performed, generally, with a brush prior to the setting into place of the tube to be worked on the machine meant for the carrying out of the process.
It has now been observed that it could prove advantageous to lubricate and to cool the inside of the tube to be worked on, and the toric mandrel which performs the work in situ during the work.